Rubber (Food Grade) Airlock Holder for use on gallon jugs or carboys that do not take screw-on fittings.Creates an air proof seal to use with the Airlocks. Can be reused, use One Step Cleanser to clean. #6 1/2 Stopper measures top 1 3/8" -bottom 1 1/8" length 1". #7 Holder measures from top 1 7/13" bottom 1 3/16" length 1". #8 1/2 Holder measures top 1 11/16",bottom 1 7/16" and again the length is 1"